Epidemiological and Clinical Characteristics Associated with Antimicrobial-Resistant Urinary Tract Infections in Outpatient and Inpatient Settings: A Retrospective Study from Northwestern Mexico

Antimicrobial resistance in urinary tract infections (UTIs) poses a critical public health challenge, yet comparative data between outpatient and inpatient settings remain limited, particularly in Latin America. This study characterized the epidemiology, microbiology, and resistance patterns of UTIs in northwestern Mexico. A retrospective analysis of 1041 patients with UTI (May-November 2024) was conducted. Microorganism identification and antimicrobial susceptibility were determined using the MicroScan WalkAway system in accordance with CLSI guidelines. Results: Outpatients accounted for 80.5% of cases and inpatients for 19.4%, with a 3.1% mortality rate. <i>Escherichia coli</i> predominated (62.9%), with a significant association with outpatients (<i>p</i> = 0.02), whereas <i>Enterobacter cloacae</i>, <i>Acinetobacter</i> spp., <i>Candida tropicalis</i>, and <i>C. albicans</i> were associated with inpatients (<i>p</i> < 0.05). Pediatric patients exhibited distinctive microbiological profiles: <i>Pseudomonas aeruginosa</i> (9.7% vs. 2.1%, <i>p</i> = 0.032), <i>Enterococcus faecalis</i> (33.3% vs. 16.2%, <i>p</i> = 0.001), and <i>Staphylococcus epidermidis</i> (26.6% vs. 6.5%, <i>p</i> = 0.027) were significantly more prevalent than in adults. Multidrug resistance (MDR) was detected in 27.1% of isolates, and extensive drug resistance (XDR) in 3.2%. XDR was associated with Gram-positive bacteria (12.2% vs. 1.4%, <i>p</i> < 0.001). Carbapenem-resistant <i>Enterobacteriaceae</i> (CRE) were identified in 0.9% (7/772) of cases, with 42.9% occurring in outpatients. Hospitalization (OR: 2.01; 95% CI: 1.43-2.83), surgical services (OR: 1.41; 95% CI: 1.02-1.97), and recent surgery (OR: 2.37; 95% CI: 1.04-5.39) were independent predictors of MDR/XDR infections. Conclusions: These findings demonstrate the emergence of CRE within the community and distinctive pediatric resistance patterns, underscoring the need for tailored antimicrobial stewardship strategies in this region.